One goal of microelectronic manufacturing is to increase the number of transistors on a device and thereby increase its operation speed. However, with increased transistor density and speed, power consumption is also increased dramatically. The heat generated from the increased power consumption can raise the microelectronic device temperature dramatically and degrade circuit performance and reliability. Therefore, reducing the overall device operation temperature is of great importance for optimum device performance.
Furthermore, operation of the transistors in a microelectronic device may cause non-uniform heating of the circuit. Certain points on the device may generate more heat than others, thus creating “hot spots”. Without such hot spots, it may be possible to increase the average power dissipation of the device while maintaining a desired temperature of the integrated circuit, thus allowing it to operate at a higher frequency.
One way to reduce hot spots is to form a layer of diamond on a device substrate, since the high thermal conductivity of diamond enables a diamond layer to spread thermal energy laterally and thus greatly minimize the localized hot spots on the device. However, there are problems associated with forming a diamond layer. Previously proposed diamond films typically exhibit numerous small grains 304 (i.e. the initial nucleation structure of the diamond film on the substrate 302), due to profuse nucleation during the initial stages of diamond growth (See FIG. 3). Large grains 306 eventually form with continued diamond growth, but the thermal conductivity of the diamond film is dictated by the more numerous, inhomogeneous small grains 304, which have a lower thermal conductivity than the large grains 306. The proliferation of small grains, whose size is on the order of 10 microns, leads to a reduction of thermal conductivity below that of single crystal diamond (2,000 W/m-K). The lower thermal conductivity of small-grain dominated diamond films in turn minimizes the small-grained films effectiveness in reducing hot spots across the device.
Accordingly, there is a need for improved methods of diamond fabrication and structures formed thereby that increase the thermal conductivity of a diamond film and thereby improve its thermal management capabilities. The present invention provides such methods and structures.